What are pigmented skin lesions?

Pigmented skin lesions refer to lesions that are brown, black or blue in colour, or may be confused with brown or black lesions (for example, vascular lesions, which sometimes look black with the naked eye but under dermatoscopy appear red, purple or blue).

What is the pigment?

The colour of pigmented skin lesions is due to:

• Melanin
• Blood
• Exogenous pigment (for example, tattoo)

What are the possible diagnoses for pigmented skin lesions?

Pigmented skin lesions are most often melanocytic. However, non-melanocytic lesions can also be pigmented, particularly in dark-skinned individuals. Non-melanocytic lesions are keratinocytic, vascular, or reactive.

Melanocytic lesions

• Benign melanocytic naevus (moles of various kinds including blue naevus)
• Melanoma

Melanocytic naevus

Congenital naevus

Blue naevus

Melanoma

Keratinocytic lesions

• Seborrhoeic keratosis
• Lentigo (freckles of various kinds including solar lentigo)
• Epidermal naevus including Becker naevus
• Pigmented basal cell carcinoma
• Pigmented actinic keratosis and intraepidermal carcinoma (also called squamous cell carcinoma in situ, Bowen disease)
• Pigmented squamous intraepithelial lesions of vulva, penis, anus
• Pigmented invasive squamous cell carcinoma

Seborrhoeic keratosis

Solar lentigo

Basal cell carcinoma

Intraepidermal carcinoma

Vascular lesions

• Trauma eg splinter haemorrhage in nail
• Purpura from bruise, capillaritis, vasculitis
• Cherry angioma
• Angiokeratoma
• Angiosarcoma
• Kaposi sarcoma

Splinter haemorrhage

Cherry angioma

Kaposi sarcoma

Angiokeratoma

Reactive pigmentation

• Dermatofibroma
• Dermatofibrosarcoma protuberans
• Postinflammatory pigmentation
• Other pigmented skin condition such as lichen planus

Dermatofibroma

Dermatofibroma

Lichen aureus

Lichen planus

Many other lesions and skin conditions are occasionally mistaken for a melanocytic or keratinocytic pigmented skin lesion.